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Does anyone know if there are markings or other indicia such as additional bolt holes visible on 1966 427/425 heads when mounted on the block with the valve covers on?. No plug wire shields are present. If so, what should I look for?
A picture or a web site showing a view of a correct head would be greatly appreciated.
As far as I know, there are no unique elements of external configuration which would differentiate the 1966 L-72 cylinder heads from many other big block cylinder heads. 1965 L-78 cylinder heads do have configuration differences which allow them to be more-or-less so-identified.
1966 Corvette L-36 and L-72 cylinder heads were equipped with spark plug barrel shields.
The mounting bosses for the barrel shields are only on the '65 and '66 heads. They are a dead giveaway, other than the obvious plug for the temp sensor used in '68-up heads. Look at an original set, and you will be able to pick them out at 10 feet.
Don - I have a set of these heads going on my 66 L72.....I sent you photos showing the spark plug shield boss...as Bill states, it's a 10 foot spot...good luck!...Craig
Thank you very much. It is an easy spot once you know what to look for. The heads on the car I'm looking at have bosses with addtional mounting holes. The fun continues...
As Bill and Craig have pointed out, and as I neglected to include in my original response, the 65-66 big block heads do have the bosses for the spark plug wire shields. However, I thought that your intention was to identify 1966 L-72 heads without reference to casting number. While 1966 L-72 heads do have the bosses for the shields, so do 1966 L-36 heads and 1966 heads used on 325 and 360 hp engines used in Chevelles and full size passenger cars. Installed on an engine, all of these heads look externally identical. Plus, the L-36 and 325/360 hp heads are FAR more common than the L-72. L-72's were built in small numbers for 1966 and used in only Covettes and a relatively small number of full size passenger cars. The same heads were also used in the 1966 Chevelle with L-78, but those cars are REALLY rare.
In any event, another "clue" as to L-72 heads in COMBINATION with the spark plug bosses would be the type of intake manifold installed on the car. If it's a Chevrolet aluminum manifold with a square bore carb flange (Holley), then it's a rectangular port manifold and consistent with L-72 heads. If it's a cast iron manifold with any carb flange configuration, then it's an oval port manifold and not consistent with L-72 rectangular port heads.
One word of caution here, though: you can't use the "manifold test" as absolute proof of the configuration of the intake ports of the heads. That's because a rectangular port intake manifold can be installed on oval port heads and an oval port manifold can be installed on rectangular port heads. It's HIGHLY bogus to mismatch intake manifolds and heads, but some folks do HIGHLY bogus things. The point is, you can't discount the possibility.
Don - Joe as always makes excellent points. The easiest thing is to quickly pop the covers and check for the 858 casting numbers...and plan to open your wallet wide....Craig
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